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[libc] Add flsll()

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Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2014-04-27 16:11:44 +01:00
parent 3ffd309375
commit d36e814b8a
4 changed files with 112 additions and 7 deletions
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50
src/arch/i386/include/bits/strings.h Normal file
View File

@@ -0,0 +1,50 @@
#ifndef _BITS_STRINGS_H
#define _BITS_STRINGS_H
FILE_LICENCE ( GPL2_OR_LATER );
/**
* Find last (i.e. most significant) set bit
*
* @v value Value
* @ret msb Most significant bit set in value (LSB=1), or zero
*/
static inline __attribute__ (( always_inline )) int __flsl ( long value ) {
long msb_minus_one;
/* If the input value is zero, the BSR instruction returns
* ZF=1 and leaves an undefined value in the output register.
* Perform this check in C rather than asm so that it can be
* omitted in cases where the compiler is able to prove that
* the input is non-zero.
*/
if ( value ) {
__asm__ ( "bsrl %1, %0"
: "=r" ( msb_minus_one )
: "rm" ( value ) );
return ( msb_minus_one + 1 );
} else {
return 0;
}
}
/**
* Find last (i.e. most significant) set bit
*
* @v value Value
* @ret msb Most significant bit set in value (LSB=1), or zero
*/
static inline __attribute__ (( always_inline )) int __flsll ( long long value ){
unsigned long high = ( value >> 32 );
unsigned long low = ( value >> 0 );
if ( high ) {
return ( 32 + __flsl ( high ) );
} else if ( low ) {
return ( __flsl ( low ) );
} else {
return 0;
}
}
#endif /* _BITS_STRINGS_H */

17
src/arch/x86/include/bits/strings.h → src/arch/x86_64/include/bits/strings.h
View File

@@ -9,8 +9,8 @@ FILE_LICENCE ( GPL2_OR_LATER );
* @v value Value
* @ret msb Most significant bit set in value (LSB=1), or zero
*/
static inline __attribute__ (( always_inline )) int __flsl ( long value ) {
long msb_minus_one;
static inline __attribute__ (( always_inline )) int __flsll ( long long value ){
long long msb_minus_one;
/* If the input value is zero, the BSR instruction returns
* ZF=1 and leaves an undefined value in the output register.
@@ -19,7 +19,7 @@ static inline __attribute__ (( always_inline )) int __flsl ( long value ) {
* the input is non-zero.
*/
if ( value ) {
__asm__ ( "bsr %1, %0"
__asm__ ( "bsrq %1, %0"
: "=r" ( msb_minus_one )
: "rm" ( value ) );
return ( msb_minus_one + 1 );
@@ -28,4 +28,15 @@ static inline __attribute__ (( always_inline )) int __flsl ( long value ) {
}
}
/**
* Find last (i.e. most significant) set bit
*
* @v value Value
* @ret msb Most significant bit set in value (LSB=1), or zero
*/
static inline __attribute__ (( always_inline )) int __flsl ( long value ) {
return __flsll ( value );
}
#endif /* _BITS_STRINGS_H */